What is the Periodic Table:
- The periodic table is a list of all known elements.
- It is arranged in order of increasing atomic number, from 1 to 106.
- The elements are arrange in such a way that atoms with the same number of shells are placed together, and atoms with similar electronic configurations in the outer shell are also placed together. This is achieved as the periodic table is arranged in rows and columns. These show the following:
Periods:
- Elements with one shell are placed in the first row (H and He).
- Elements with two shells are placed in the second row (Li to Ne) and so on.
- A row of elements thus arranged is called a period.
Groups:
- Elements are aligned vertically (in columns) with other elements in different rows, if they share a similar outer-shell electronic configuration.
- Elements with outer-shell configuration ns¹ are all placed in the same column (Li, Na, K, Rb, Cs, Fr).
- A column of elements thus arranged is called a group.
Exceptions:
- Since the electronic configurations of H and He are unusual, they do not fit comfortably into any group.
- They are thus allocated a group based on similarities in physical and chemical properties with other members of the group.
- He is placed in group 0 on this basis, but hydrogen does not behave like any other element and so is placed in a group of its own.
- The elements Ce-Lu and Th - Lw belong in the periodic table between group 2 and the transition metals but if they are placed there periods 6 and 7 do not fit onto a page of a4, so they are placed below the other elements in most tables.
The Orbital Blocks - S/P/D/F:
- All elements belong to one of four main blocks: the s-block, the p-block, the d-block and the f-block.
- The s-block elements are all those with at least one s-electron in their outer shell.
- The p-block elements are all those with at least one p-electron in their outer shell.
- The d-block elements are all those with at least one d-electron and at least one s-electron but no f or p-electron in their outer shell.
Periodicity:
- The Study of Periodic Trends is known as Periodicity.
- Periodic Trends are trends shown between elements in the periodic table.
- The physical and chemical properties of elements in the Periodic Table show clear patterns related to the position of each element in the Periodic Table.
- Elements in the same group show similar properties, and properties change gradually on crossing a period.
- As atomic number increases, the properties of the elements show trends which repeat themselves in each period of the periodic table.